/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 *
 */
package com.github.dcevm;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Type;

import java.io.*;
import java.lang.instrument.UnmodifiableClassException;
import java.net.URL;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * @author Thomas Wuerthinger
 * @author Kerstin Breiteneder
 * @author Christoph Wimberger
 * @author Ivan Dubrov
 */
public class HotSwapTool {

  /**
   * Prefix for the version number in the class name. The class bytes are modified that this string including
   * the following number is removed. This means that e.g. A___2 is treated as A anywhere in the source code. This is introduced
   * to make the IDE not complain about multiple defined classes.
   */
  public static final Pattern VERSION_PATTERN = Pattern.compile("___([0-9]+)");
  public static final Pattern VERSION_MATCH = Pattern.compile(".*(___([0-9]+))$");
  private static final String CLASS_FILE_SUFFIX = ".class";
  private static Map<Class<?>, Integer> currentVersion = new Hashtable<Class<?>, Integer>();
  private static Redefiner redefiner;
  private static int redefinitionCount;
  private static long totalTime;

  static {
    try {
      //redefiner = new JDIRedefiner(4000);
      redefiner = new InstrumentationRedefiner();
    } catch (Exception e) {
      throw new IllegalStateException(e);
    }
  }

  /**
   * Returns the current version of the inner classes of a specified outer class.
   *
   * @param baseClass the outer class whose version is queried
   * @return the version of the inner classes of the specified outer class
   */
  public static int getCurrentVersion(Class<?> baseClass) {
    if (!currentVersion.containsKey(baseClass)) {
      currentVersion.put(baseClass, 0);
    }
    return currentVersion.get(baseClass);
  }

  /**
   * Performs an explicit shutdown and disconnects from the VM.
   */
  public static void shutdown() throws IOException {
    redefiner.close();
    redefiner = null;
  }

  private static Map<Class<?>, byte[]> buildRedefinitionMap(Map<String, File> classes) throws IOException, ClassNotFoundException {
    // Collect rename rules
    // Also, makes sure all classes are loaded in the VM, before they are redefined
    final Map<String, String> typeMappings = new HashMap<String, String>();
    for (String name : classes.keySet()) {
      Class<?> clazz = Class.forName(name); // FIXME: classloader?
      ClassRedefinitionPolicy policy = clazz.getAnnotation(ClassRedefinitionPolicy.class);
      Class<?> replacement = (policy != null && policy.alias() != ClassRedefinitionPolicy.NoClass.class) ?
              policy.alias() : clazz;
      typeMappings.put(Type.getInternalName(clazz), stripVersion(Type.getInternalName(replacement)));

    }

    Map<Class<?>, byte[]> classesMap = new HashMap<Class<?>, byte[]>();
    for (File file : classes.values()) {
      loadAdaptedClass(file, typeMappings, classesMap);
    }
    return classesMap;
  }

  private static void loadAdaptedClass(File file, Map<String, String> typeMappnigs, Map<Class<?>, byte[]> result) throws IOException, ClassNotFoundException {

    ClassWriter writer = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);
    TestClassAdapter adapter = new TestClassAdapter(writer, typeMappnigs);

    InputStream in = new FileInputStream(file);
    try {
      new ClassReader(in).accept(adapter, ClassReader.EXPAND_FRAMES);
    } finally {
      try {
        in.close();
      } catch (IOException e) {
        // Ignore.
      }
    }
    byte[] bytes = writer.toByteArray();
    String className = adapter.getClassName().replace('/', '.');
    result.put(Class.forName(className), bytes); // FIXME: ClassLoader...
  }

  /**
   * Redefines all inner classes of a outer class to a specified version. Inner classes who do not have a particular
   * representation for a version remain unchanged.
   *
   * @param outerClass    the outer class whose inner classes should be redefined
   * @param versionNumber the target version number
   */
  public static void toVersion(Class<?> outerClass, int versionNumber, Class<?>... extraClasses) {
    assert versionNumber >= 0;

    if (versionNumber == getCurrentVersion(outerClass)) {
      // Nothing to do!
      return;
    }

    Map<String, File> files = findClassesWithVersion(outerClass, versionNumber);

    for (Class<?> extra : extraClasses) {
      if (parseClassVersion(extra.getSimpleName()) == versionNumber) {
        String packageName = extra.getPackage().getName().replace('.', '/');
        URL url = extra.getClassLoader().getResource(packageName);
        if (url == null) {
          throw new IllegalArgumentException("Cannot find URL corresponding to the package '" + packageName + "'");
        }
        File file = new File(url.getFile(), extra.getSimpleName() + ".class");
        files.put(extra.getName(), file);
      }
    }

    try {
      Map<Class<?>, byte[]> map = buildRedefinitionMap(files);

      long startTime = System.currentTimeMillis();
      redefiner.redefineClasses(map);
      long curTime = System.currentTimeMillis() - startTime;
      totalTime += curTime;
      redefinitionCount++;

    } catch (UnmodifiableClassException e) {
      throw new UnsupportedOperationException(e);
    } catch (ClassNotFoundException e) {
      throw new RuntimeException("Cannot redefine classes", e);
    } catch (IOException e) {
      throw new RuntimeException("Cannot redefine classes", e);
    }

    setCurrentVersion(outerClass, versionNumber);
  }

  private static Map<String, File> findClassesWithVersion(Class<?> baseClass, int version) {
    Map<String, File> classes = new HashMap<String, File>();

    String packageName = baseClass.getPackage().getName().replace('.', '/');
    URL url = baseClass.getClassLoader().getResource(packageName);
    if (url == null) {
      throw new IllegalArgumentException("Cannot find URL corresponding to the package '" + packageName + "'");
    }
    File folder = new File(url.getFile());
    for (File f : folder.listFiles(IsClassFile.INSTANCE)) {
      String simpleName = f.getName().substring(0, f.getName().length() - CLASS_FILE_SUFFIX.length());
      String name = baseClass.getPackage().getName() + '.' + simpleName;

      if (isInnerClass(name, baseClass) && parseClassVersion(simpleName) == version) {
        classes.put(name, f);
      }
    }
    return classes;
  }

  private enum IsClassFile implements FilenameFilter {
    INSTANCE;

    @Override
    public boolean accept(File dir, String name) {
      return name.endsWith(CLASS_FILE_SUFFIX);
    }
  }

  private static boolean isInnerClass(String name, Class<?> baseClass) {
    return name.startsWith(baseClass.getName() + "$");
  }

  private static void setCurrentVersion(Class<?> baseClass, int value) {
    currentVersion.put(baseClass, value);
  }

  /**
   * Parse version of the class from the class name. Classes are named in the form of [Name]___[Version]
   */
  private static int parseClassVersion(String simpleName) {
    Matcher m = VERSION_MATCH.matcher(simpleName);
    return m.matches() ? Integer.valueOf(m.group(2)) : 0;
  }

  private static String stripVersion(String className) {
    Matcher m = VERSION_MATCH.matcher(className);
    if (m.matches()) {
      return className.substring(0, m.start(1)) + className.substring(m.end(1));
    } else {
      return className;
    }
  }

  public static void resetTimings() {
    redefinitionCount = 0;
    totalTime = 0;
  }

  public static int getRedefinitionCount() {
    return redefinitionCount;
  }

  public static long getTotalTime() {
    return totalTime;
  }
}
